This invention relates to a fuel injection system and more particularly to a fuel injection system including a sub injector and an improved location and orientation for such a sub injector.
The use of direct fuel injection in two cycle crankcase compression internal combustion engines is realized as a way in which the emissions and economy of such engines can be controlled. However, it has been found that if all of the fuel for the engine running is injected directly into the cylinder, that certain problems may arise. Specifically, the crankcase and piston may not be adequately cooled under high speed high load running conditions. Normally, fuel is introduced in a two cycle crankcase compression engine through the crankcase and this fuel in the crankcase and its vaporization tends to cool the lower end of the engine and the underside of the piston. However, if all of the fuel is directly injected, then this cooling does not result and certain overheating problems may be encountered.
Also, the use of a single fuel injector and direct fuel injection has been found not to provide the adequate control for the fuel as may be desired under some conditions. That is, if a single, direct fuel injector is employed, it may not be possible to provide the desired fuel control and maximum power output.
To offset the deficiencies as aforenoted, it has been proposed to provide an arrangement wherein a sub injector is provided that will inject fuel into the induction system or crankcase under high speed and high load conditions to supplement the fuel that is supplied directly to the combustion chamber by the main injector. However, the use of such sub injectors gives rise to certain other problems.
Specifically, if a multiple cylinder engine is employed, it is desirable to provide only a single sub injector for all cylinders so as to reduce costs. However, the previously proposed systems have provided some difficulty in insuring adequate mixture distribution from the sub injector to all cylinders under high speed conditions. In addition, since the sub injector normally operates only at high speed conditions, prolonged periods of low speed running can give rise to plugging or clogging of the sub injector. This occurs due to the blow back of gases from the crankcase into the induction system, even when flow controlling check valves are employed.
It is, therefore, a principal object of this invention to provide an improved fuel injection system for a two cycle crankcase compression engine employing a sub injector and wherein a single sub injector can serve multiple cylinders and good mixture distribution is insured.
It is a further object of this invention to provide a sub injector arrangement for the two cycle crankcase compression internal combustion engine wherein the sub injector will be protected from deposits, particularly during the times when it is not injecting fuel.